3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), that is, the improvement of an LTE Universal Mobile Telecommunications System (UMTS), has been introduced as 3GPP release 8. 3GPP LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) in downlink and uses Single Carrier-Frequency Division Multiple Access (SC-FDMA) in uplink. 3GPP LTE adopts Multiple Input Multiple Output (MIMO) having a maximum of 4 antennas. Recently, 3GPP LTE-Advanced (LTE-A), that is, the evolution of 3GPP LTE, is being discussed.
A Minimization Drive Test (MDT) is that service providers perform a test using UE instead of a vehicle for coverage optimization. Coverage varies depending on the location of a BS, the deployment of peripheral buildings, and a user use environment. Accordingly, a service provider needs to periodically perform a driving test, and lots of costs and resources are consumed. An MDT is that a service provider measures coverage using UE.
An MDT can be divided into a logged MDT and an immediate MDT. In accordance with the logged MDT, UE performs MDT measurement and then transfers logged measurement to a network at a specific point of time. In accordance with the immediate MDT, UE performs MDT measurement and then transfers measurement to a network when a report condition is satisfied. In the logged MDT, MDT measurement is performed in an RRC idle mode, whereas in the immediate MDT, MDT measurement is performed in an RRC connected mode.
Meanwhile, in a wireless communication system, the usage of a wireless network can be suddenly increased at a specific time. In this case, to measure radio environments or UE capability criteria for a specific time, log the radio environments or UE capability criteria, and report the log can be preferred. Furthermore, if UE reports a logged measurement result to a network during the time when the usage of a wireless network is suddenly increased, a problem in which the congestion of a wireless communication network is further increased can occur. Suitability in executing logging and/or a report by UE can vary in each time interval as described above. Accordingly, there is a need for a method in which UE performs an MDT or reports radio link failure information suitably for a wireless communication network situation.